Toward a Fast and Secure Blockchain Framework for Smart Contracts

随着加密货币的成功，区块链最近也在发展 转变为一个技术平台，支持安全、分散和一致的 互联网规模的交易分类账。 智能合约部署是最 许多区块链系统的重要特征。用户可以开发智能合约 对任意复杂的交易规则进行编码， 区块链系统。合同（即，交易规则）， 由系统的所有参与者忠实地执行和执行， 未来编码交易的任何潜在对手方风险。 采用智能合约技术的一个挑战是安全性 风险因为智能合约实际上是直接操纵 数字资产，确保这些合同的正确性非常关键。 不幸的是，人类程序员经常犯错误和错误。的 smart中的编程错误和安全漏洞的后果 合同特别严重，往往导致数千万美元的损失， 损失采用的另一个挑战是性能问题。确保 交易分类账的一致性， 区块链系统必须以缓慢的块生成来运行，以避免 并发块（即，分叉），这被认为是有害的共识 安全为代价的因此，这些系统具有非常有限的交易吞吐量， 智能合约用户往往要等待很长一段时间才能确认 一笔交易 为了应对安全挑战，我们建议设计一套新的工具， 保护智能合约，将静态分析与运行时相结合 仪器。一个观察是，事务执行不是 区块链平台的瓶颈。相反，瓶颈首先出现在 共识协议，然后在区块链存储层。因此 运行时插装的开销，这对于其他 域，实际上对于智能合约来说可以忽略不计。为了解决这个问题 挑战，我们建议设计一种新的共识协议， 块到直接非循环图中，以安全地合并并发块。的 协议固有地编码两种策略，一种是乐观策略， 性能和保守策略，确保共识进展到 阻止活性攻击。我们还建议重新考虑仓库的设计 层和事务传播来构建高性能的端到端 区块链平台。 如果这项研究取得成功，所提出的技术将使 智能合约的开发更加安全。的技术 还将允许区块链平台以更高的速度处理智能合约， 吞吐量和更快的速度。拟议研究的最终目标是 找到全面的解决方案，充分发挥智能合约的潜力 技术.

Following the success of the cryptocurrencies, blockchain has recently evolved into a technology platform that powers secure, decentralized, and consistent transaction ledgers at Internet-scale. Smart contract deployment is the most important feature of many blockchain systems. Users can develop smart contracts to encode arbitrarily complicated transaction rules and deploy these contracts to a blockchain system. The contracts (i.e., transaction rules) are then faithfully executed and enforced by all participants of the system, eliminating any potential counter-party risk of the encoded transactions in future. One challenge for the adoption of smart contract techniques is the security risk. Because smart contracts are in fact programs that directly manipulate digital assets, ensuring the correctness of these contracts is very critical. Unfortunately, human programmers often make mistakes and errors. The consequence of programming errors and security vulnerabilities in smart contracts is particularly severe, often leading to tens of millions of dollar losses. Another challenge for the adoption is the performance issue. To ensure the consistency of the transaction ledger, the consensus protocols in blockchain systems have to operate with slow block generation to avoid concurrent blocks (i.e., forks), which are considered harmful for the consensus safety. Therefore these systems have very limited transaction throughputs for smart contracts. Users often have to wait for a long period of time to confirm a transaction. To tackle the security challenge, we propose to design a new set of tools for securing smart contracts, combining the static analysis with runtime instrumentations. One observation is that the transaction execution is not the bottleneck in blockchain platforms. The bottleneck is instead first at the consensus protocol and then at the blockchain storage layer. Therefore the overhead of runtime instrumentation, which is often too expensive for other domains, is in fact negligible for smart contracts. To tackle the performance challenge, we propose to design a novel consensus protocol that reorganizes blocks into direct acyclic graph to safely incorporate concurrent blocks. The protocol inherently encodes two strategies, an optimistic strategy for high performance and a conservative strategy that ensure the consensus progress to thwart liveness attacks. We also propose to revisit the design of the storage layer and the transaction propagation to build a high performance end-to-end blockchain platform. If the proposed research becomes successful, the proposed techniques would make the development of smart contracts significantly more secure. The techniques would also allow blockchain platforms to process smart contracts at a higher throughput and a faster speed. The ultimate goal of the proposed research is to find comprehensive solutions to unleash the full potential of smart contract technologies.